This invention is an improvement in the type of dual purpose gynecological instrument which is used both to obtain axial uterine measurements and to obtain a width profile of the uterus.
Instruments of this type are exemplified by the present inventor's own prior art U.S. Pat. No. 3,706,307. This patent shows an elongated uterine probe assembly comprising a rod cylindrically surrounded by a flexible plastic sleeve formed with short longitudinal slits. This probe is used to sound the entire depth of the uterus, i.e., the entire depth of the cervical canal and endometrial cavity, by inserting it to the depth of the fundus (the back wall of the uterus). It is also used to locate the position of the uterine isthmus or cervical isthmic region, and therefore to determine cervical length. The rod is retracted by a predetermined amount so as to foreshorten the plastic sleeve while the probe is still within the uterus. This causes the plastic sleeve to collapse laterally outwardly a predetermined distance to form radially extending wings. The slits formed in the sleeve facilitate this collapse. The probe is then withdrawn until the extended wings make contact with the walls of the uterus at the level of the uterine isthmus, preventing any further withdrawal, and the depth of the insertion is noted. This second measurement represents the effective length of the cervix which includes the cervical canal, isthmus and a variable small portion of the lower uterine segment.
While the aforementioned observation would tell the gynecologist that at that particular depth of insertion the uterus has a width equal to the predetermined "wing spread" of the instrument, it does not permit the gynecologist to extrapolate the shape or width dimensions of the uterine cavity on the basis of the fragmentary information obtained. Thus the instrument of the inventor's own prior art was designed essentially to determine individual axial uterine dimensions of total uterine length, and the length of the endometrial cavity by taking the cervical length and subtracting the cervical length from the whole uterine length. The instrument thus measures only axial dimensions and does not and is not intended to measure uterine width.
A uterine caliper which enables width measurements is disclosed in King, et al. U.S. Pat. No. 4,016,867. This caliper has outwardly biased resilient caliper wings and a spring-loaded slidable cervical stop. A slide on the body is operatively connected to the wings by a monofilament and operates with respect to a first scale on the body as a width indicator. The wings may be allowed to open by moving the slide, and when the wings engage the utero-tubal junctions, the width may be read on the first scale.
The present inventor has found that it would be desirable to have relatively complete information from which one can extrapolate the shape and width dimensions of the endometrial cavity. It would therefore be desirable to improve the depth-width probes described above so that they are capable of measuring axial uterine dimensions as well as the insertion depths at which the width of the uterus matches a plurality of different predetermined wing spreads of the expandable probe.
But in trying to accomplish that objective, a second problem arises. The prior art single width probe described above needs only a simple and inexpensive mechanism for retracting the foreshortening rod to a single stable position at which the wings collapse outwardly to the predetermined width. Consequently, the entire instrument, including both the probe and the wing-actuating mechanism therefor, is economically disposable.
However, a multiple-position wing actuating mechanism is necessarily more complex and expensive than its single-position prior art counterpart. Therefore, with an improved probe of the kind contemplated herein there would be considerable reluctance to dispose of the entire instrument, including the more expensive wing-actuating mechanism. It would be desirable, instead, for the probe assembly to be removable and replaceable so that it alone is disposable, and the actuating mechanism is not.
There is one further complicating factor. Recall for a moment that the probe assembly consists of two separate parts, the collapsible sleeve and the foreshortening rod, which must be movable relative to each other in order to accomplish the foreshortening operation which expands the wings. Thus the provision for removable and replaceable connection of the disposable probe assembly to the permanent portion of the instrument must somehow connect these two probe components to two respective independently movable parts of the permanent assembly.